Swaging screw-threads.



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SALOMON FRANK, OF FRANKFORT-ON-THE-h/IAIN, GERMANY.

SWAGING SCREW TH READS.

$PECIFICATION forming part of Letters Patent No. 638,962, dated December 12, 1899. Application filed July 1, 1899. Serial No. 722,530. No Specimens.)

To on whom it may concern:

Be it known that I, SALOMON FRANK, a subject of the Queen of England, and a resident the object of this process is to provide tubes or otherhollow cylindrical articles with screw threads, either Within or without, by forcing a matrix or die of corresponding shape into the wall of the tube or the like.

In carrying out my invention I preferably change or vary the diameter of the portion of the tube to be operated upon, as by expanding or contracting it, and then simultaneously restore said portion to its original diameter and form screw-threads thereon, as by placing the contracted portion within an interiorly-screw-ihreaded die and expanding it against the screw-threads by a smooth die or plunger or by contracting the expanded portion against a screw-threaded mandrel by drawing it and the mandrel through a perforated die.

In the accompanying drawings, Figures 1 and 2 are sectional views of one form of apparatus employed to form the external and internal threads, respectively; and Fig. 3 is a similar View of the means employed for forming a screw-threaded cap.

Fig. 1 illustrates the manner in which a tube 1) is by this process provided with an outer screw-thread. To this end one extremity of the tube is first reduced somewhat in width by means of a draw-plate, so that it may readily fit in the matrix a, having the desired screw-thread formed in its interior. A die or mandrel c is then driven into the end of the tube, which will force the metal of the tube against the screw-threads, and thereby form the required threads upon the exterior of the tube. The diameter of the mandrel is substantially the same as the original diameter of the tube, so that it will just clear the same, and thus leave the interior diameter of the tube c, is forced through the matrix a, the aper ture whereof is equal to the outer diameter of the tube 1), the metal of the tube will be pressed into the convolutions of the screwi thread of c. The tube is now provided with the required screw thread and die or mandrel c is screwed out of it.

Fig. 3 shows how this process applies to the inner screw-threading or tapping of a cap or lid of any receptacle. first been slightly enlarged at its edge, so as After the lid 12 has to be capable of accurately accommodating a screw-threaded die 0 the said lid or cap b is placed upon a matrix of corresponding shape and forced down into it in the same Way as has been described with reference to Fig. 2. The lid, cap, or cover thus tapped is then screwed off the die.

Having now particularly described and ascertained the nature of this invention and in What manner the same is to be performed, I declare that what I claim is- 1. The method substantially as herein described, offormin g screw-threads upon tubes, which consists in varying the original diameter of the portion of the tube to be threaded, and then simultaneously restoring the diameter of said portion of the tube and forming screw-threads thereon.

i 2. The method substantially as herein described, of forming internal screw-threads upon tubes, which consists in expanding the portion of the tube to be threaded, and then simultaneously contracting said portion of the tube and forming screw-threads thereon.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

SALOMON FRANK. 

